When a mobile station (MS) is in the cell-edge region, it may be able to receive signals from multiple base stations (BSs) and the MS's transmission may be received at multiple BSs regardless of the traffic load. To avoid inter-cell-interference, if the multiple BSs are coordinated, the downlink or uplink performance can be increased significantly. Therefore, the inter-BS cooperation technique in 4G, which is called multicell MIMO (multi-BS MIMO) in WiMAX and Coordinated Multi-Point transmission/reception (CoMP) in 3GPP are presented in their respective specification.
In cell-based MIMO downlink communications, it is necessary to design precoding matrices that are able to suppress inter-cell-interference to other cell users. Multi-BS MIMO technique, which improves sector throughput and cell-edge throughput through multi-BS cooperation, can alleviate the effect of inter-cell-interference based on precoding matrix coordination. For codebook-based feedback, MS finds Preferred Matrix Indexes (PMIs) from the codebook, one of which acts as the strongest signal power from the serving base station (serving BS) and the others are PMIs which act as the weakest interference from the neighboring BSs. Then based on the feedback of PMIs from MSs to their respective serving BSs, the inter-cell interference can be mitigated by coordinating the precoders applied in neighboring cells via backhaul signaling.
In the conventional precoder selection criteria, the candidates for PMI selection set at MSs are restrained according to inter-BS's negotiation, hence prevent the inter-cell-interference. However, the selection of PMI will be confined to the pre-defined codebook.
In summary, a need exists in the art to provide a solution that can effectively and flexibly prevent the inter-cell-interference, so as to improve the communication quality of the multi-input multi-output network.